The invention relates to a bearing comprising at least one bearing ring on which a raceway is formed.
Whenever in this document the word bearing is used, it shall be understood to include also bearing units, which may comprise more than one bearing. When rings are mentioned, these rings may comprise also non-annular parts such as flanges with ears and bolt holes, e.g. for mounting the bearing or ring into its application. Bearings include sliding bearings and rolling bearings of different kinds, such as ball bearings, taper roller bearings, cylindrical roller bearings, spherical roller bearings, etc.
Bearings are used in very many different applications, for transferring forces or loads from rotating parts to stationary parts and/or vice versa. Each application has its own operating conditions and hence will put its own requirements to the capabilities and functionality of the bearing. To enable the bearing to transfer an important force or load, most bearings are formed from so called bearing steel, which is highly alloyed steel, with capabilities to be hardened to quite high hardness. This will give the bearing a high strength that it needs to be able to transfer the high loads required.
Certain bearing applications are strongly influenced by the weight of the bearing and do require the bearing to have as low a weight as possible. Sometimes this requirement is combined with the requirement that the bearing is corrosion resistant. Such requirements are found e.g. in the aircraft industry and the food industry.
U.S. Patent application US 2002/0191878 describes a bearing where the bearing rings are formed of a kind of titanium alloy with a ceramic film on the raceway and the rolling elements are formed of a ceramic material. These materials do fulfil the requirements regarding reduced weight as well as regarding corrosion resistance to a large extent. However material such as titanium is usually not strong enough to sustain the loads required. This is equally valid for a ceramic film.
UK Patent application GB 2 285 490 describes a bearing member, notably a constant velocity joint, where the bearing tracks are provided by a rigid porous ceramic insert, infiltrated with light metal alloy in the pores, the remainder of the outer member being formed of said light metal alloy. However a porous ceramic insert is not able to withstand loads such as they occur e.g. in raceways of roller bearings.
It is an aim of the present invention to provide a bearing that is lightweight, has good corrosion resistance and also has the capability to carry high loads, such a occur in raceways of roller bearings.